Broadly speaking, the invention relates to a peripheral coder/decoder (codec) that has low power consumption such that the peripheral codec facilitates bus-powered peripheral devices that utilize a codec. One such peripheral device is a modem. In the case of host-based modem, a host computer provides processing capabilities while a bus-powered peripheral device contains circuitry for analog-to-digital and digital-to-analog conversions as well as circuitry for interfacing to a transmission media. The bus-powered peripheral device is coupled to the host computer by a peripheral bus. In one embodiment, the peripheral bus is a Universal Serial Bus (USB) bus and the bus-powered peripheral device is a USB device.
The invention can be implemented in numerous ways, including as a system, a device, an apparatus, and a method. Several embodiments of the invention are summarized below.
As a computer system, one embodiment of the invention includes a computer including a microprocessor, memory and a bus host controller; a bus operatively connected to the computer, the bus being controlled by the bus host controller; and a codec apparatus operatively connected to the computer via the bus, the codec apparatus being completely powered by the bus. Optionally, the codec apparatus is a codec modem and the bus is a serial bus such as a USB bus.
As a USB codec modem peripheral device that uses a host processor for modulation and demodulation processing, an embodiment of the invention includes: a USB bus interface coupled to the host processor via a USB bus; a codec that performs analog-to-digital conversions on incoming signals and digital-to-analog conversions on outgoing signals; and a hybrid circuit that couples the outgoing signals to a transmission medium and couples incoming signals to the transmission medium. Preferably, the USB codec modem is bus-powered by the USB bus, the USB codec modem peripheral device does not include modem circuitry that performs modulation and demodulation operations, and the host processor implements modulation and demodulation operations.
As a method for transmitting and receiving signals using a modem, an embodiment of the invention includes the operations of: coupling a peripheral apparatus having a codec portion of the modem to a peripheral bus of a computer system, the peripheral apparatus lacking capability to perform modulation and demodulation processing; performing modulation and demodulation processing for the modem at a microprocessor of the computer system; and performing codec processing at the codec portion of the peripheral apparatus. The peripheral apparatus is powered exclusively through the peripheral bus.
The advantages of the invention are numerous. One advantage of the invention is that a bus-powered peripheral codec is made available. Examples are a modem codec, a video codec, a pulse coded modulation (PCM) codec, and the like. The peripheral codec is a peripheral device that couples to a computer over a bus, such as a USB bus, and does not require any external power source other than the power provided over the bus itself. Another advantage of the invention is that the peripheral codec has a low gate count and manageable power consumption such that the peripheral codec is able to be bus-powered. Still another advantage of the invention is that, in the case of bus-powered devices, the low power utilization of the peripheral codec prolongs battery life due to its low power consumption. Yet another advantage of the invention is that, in the case where the peripheral codec is used to form a modem codec, the peripheral codec can facilitate remote wakeup of the host computer and/or the peripheral codec based on external events.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.